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IsBipartite.java
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IsBipartite.java
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class IsBipartite {
// 1. dfs
public boolean isBipartite(int[][] graph) {
if (graph == null || graph.length == 0) {
return false;
}
int n = graph.length;
int[] visited = new int[n]; // 0: not visited 1: color1 -1: color2
for (int i = 0; i < n; i++) {
if (visited[i] == 0 && !isValidDFS(i, 1, graph, visited)) {
return false;
}
}
return true;
}
private boolean isValidDFS(int node, int color, int[][] graph, int[] visited) {
if (visited[node] != 0) {
return visited[node] == color;
}
visited[node] = color;
for (int nei : graph[node]) {
if (!isValidDFS(nei, graph, -color, graph, visited)) {
return false;
}
}
return true;
}
// 2. bfs
public boolean isBipartite1(int[][] graph) {
if (graph == null || graph.length == 0) {
return false;
}
int n = graph.length;
int[] visited = new int[n];
for (int i = 0; i < n; i++) {
if (visited[i] == 0 && !isValidBFS(i, graph, visited)) {
return false;
}
}
return true;
}
private boolean isValidBFS(int node, int[][] graph, int[] visited) {
Queue<Integer> queue = new ArrayDeque<>();
queue.offer(node);
visited[node] = 1;
while (!queue.isEmpty()) {
int cur = queue.poll();
int color = visited[cur];
for (int nei : graph[cur]) {
if (visited[nei] == color) {
return false;
}
if (visited[nei] == 0) {
queue.offer(nei);
visited[nei] = -color;
}
}
}
return true;
}
}